1. Field of the Invention
The present invention relates to systems and methods for contraband detection/identification that employ modalities incorporating Gamma Resonance Absorption, Gamma Resonance Fluorescence, Gamma Induced Photofission, and Dual Beam Gamma Energy Absorptiometry techniques and combinations thereof in a single system.
2. Description of the Prior Art
Systems for detecting nitrogen based elements in contraband materials are fairly well known. These systems basically utilize the irradiation of such materials with gamma rays and the detection of gamma rays emitted or absorbed by the materials after subjecting them to the input gamma rays of specific energy to be preferentially absorbed or to induce fluorescence in the specific elemental material being detected. One technique of such detection is Gamma Resonance Absorption (GRA) analysis. This type of system generally utilizes the effect of gamma ray absorption by the nucleus of the objects being interrogated during irradiation. The concentration of these gamma rays are detected by gamma ray detectors or arrays of detectors and the signals analyzed to determine the concentrations of chemical elements which make up the object being interrogated. These elements are found in explosives or illicit drugs in differing quantities, ratios and concentrations. By calculating and determining the ratios and concentrations, it is possible to identify and differentiate targeted contraband substances.
In such Contraband Detection Systems (CD or CDS), an example of which is shown in FIG. 1(a), a proton beam 10 is generated that is directed to a proton beam target device 12 that generates a gamma ray fan 15 that is directed to a target object 20 such as a rotating baggage container. Such a GRA CDS system is described in U.S. Pat. No. 5,784,430 the whole contents and disclosure of which is incorporated by reference as if fully set forth herein. Such CD systems are distinguishable by the manner in which the proton beam is generated: 1) Electrostatic Accelerator based, and 2) RF Accelerator based. An early form of the Electrostatic Accelerator based CDS comprises a high current (e.g., 10 mA) electrostatic accelerator, a specially designed proton beam target 12 for gamma generation, and a detector such as segmented and arrayed Bismuth Germinate (BGO) detectors 25. The accelerator produces a beam of protons 10, e.g., at energies of about 1.75 MeV, with a very narrow energy spread. As shown in FIG. 1(b), this high energy proton beam is bombarded onto the specially designed target 12 which is coated with a thin film of 13C (of about 1 micron thick) to generate resonant gamma rays 15a at an energy of about 9.17 MeV by the reaction 13C(ρ,γ)14N and, additionally, generates non-resonant gamma emissions 15b. The resultant gamma rays 15a are preferentially absorbed by 14N in explosives-type contraband. The penetrating power of the gamma rays combined with a tomographic detection scheme allows 3-D images of the total density and select element density in the interrogated cargo/luggage/container to be generated which is then utilized to detect for the presence of concealed explosives utilizing the ratio of resonant to non-resonant absorption thereby providing the ratio of Nitrogen density to total density.
With the on-going threat of terrorism all over the world, the need has come for improved means of detecting contraband materials, including nitrogen and nuclear containing explosives that may be concealed in vehicles such as cars, trucks automobiles, shipping containers, airplanes, etc. This requires the implementation of improved proton beam target devices. The need has also come for a versatile, multi-mode, single CDS that employs a variety of non-invasive active and passive detection techniques that can be used for detecting a variety of target materials, including nuclear materials.
It would thus be highly desirable to provide a Contraband Detection System and methodology incorporating numerous means in combination as a single stand alone system or, operated as separate systems with single or multiple capabilities utilizing single or multiple non-intrusive active gamma beam probes to detect, analyze and/or image the contents of objects, e.g., shipping containers, cargo, parcels, luggage, trucks, vehicles, railroad cars, mail, checkpoints, border crossings etc.
It would be further highly desirable to provide a CDS and methodology providing a non-intrusive, single scan means for detecting explosives, nuclear bombs and nuclear materials, shielding of nuclear or other materials, drugs, chemical warfare agents and other contraband of interest. The detection can be utilized in various configurations including inline, portal, remote and standoff.
It would be additionally desirable to provide a CDS and methodology for providing a non-intrusive, single pass/multiple scan means for detecting explosives, nuclear bombs and nuclear materials, shielding of nuclear or other materials, drugs, chemical warfare agents and other contraband of interest. The detection can be utilized in various configurations including inline, portal, remote and standoff.
It would be highly desirable to provide a novel proton beam target design of increased durability that is capable of better withstanding impact of high energy proton beams utilized in the generation of gamma rays for such CDS systems.